Aquatic animal production has reached 130.9 million tons, with over 89% destined for human consumption. The remaining portion is dedicated to producing fishmeal and fish oil. It is crucial to recognize that feed-related expenses constitute 40-70% of total costs within the aquaculture sector, mainly due to the reliance on fishmeal. Both soybean meal and fishmeal stand as the cornerstone ingredients in aquafeed formulations. Considering this, numerous studies are actively exploring innovative alternative ingredients to reduce this dependence on traditional fishmeal and soybean meal. This chapter delves into the most researched alternative feed ingredients, spotlighting their nutritional benefits. It describes several by-products that have been proposed as sources for aquafeeds. Furthermore, it examines the essential additives incorporated into aquafeeds to ensure these alternatives are nourishing and suitable for aquatic life. Additionally, the chapter showcases remarkable biotechnological advancements emerging from recent research, which impact economic efficiency and production costs in the industry.